Various devices in automoiles and other similar carriers are provided with a so-called "memory" capability. Perhaps the best known of these devices is the memory power seat in an automobile. There, one or more predetermined positions for the seat are determined and set in a memory by the operator. Subsequent actuation of a particular "recall" switch serves to automatically move the seat from its present, or actual, position to the selected, or recalled, position stored in memory. A powered automobile seat typically is moved along or around three or more axes by respective motors, and a memory system may operate to automatically position the seat anywhere within the range of travel embraced by those motors and their associated drive systems. Examples of such memory seat control systems may be found in U.S. Pat. Nos. 4,434,468; 4,463,426 and 4,510,426. In each of the memory seat systems disclosed by those patents, a sensor is associated with each of the drive motors or the associated driving apparatus for providing pulses indicative, either directly or indirectly, of variations in the position of the associated drive train and thus, the seat. In addition to automobile seats being provided with a "memory" capability, other devices such as mirrors and the like may also automatically be positioned to locations previously stored in a memory associated with the control. Still other devices within an automobile may possess a characteristic which may be physically varied by electronic control, which characteristic is capable, directly or indirectly, of being stored in and recalled from a memory. One example of this latter type of device includes the variably-inflatable air bladders which may be placed in an automobile seat for adjusting contour and firmness.
The electronic control systems associated with the aforementioned type memory devices, and particularly the memory seat controls systems described in the aforementioned patents, advise the central control system of the actual position of the seat drive apparatus on a substantially continuous basis. Thus, if a position pulse is generated for each revolution of a drive motor, that pulse is immediately entered and counted in the central controller such that that controller constantly knows the position of the seat and may stop its motion when it arrives at the "recalled" position. While such arrangement is readily possible in a system in which all of the logic and circuitry associated with the control is dedicated only, or nearly only, to the control of the memory seat, such may not be the case where the control circuitry is called upon to control a number of functions, as for example in the multiplex control systems being developed to serve a relatively large number of diverse automobile body electrical functions. Examples of such vehicle multiplex control systems are found in U.S. Pat. Nos. 4,528,662 and 4,534,025, assigned to the same assignee as the present application. In those multiplex control systems, a variety of inputs and outputs associated with the vehicle electrical system are extended respectively to and from the central controller via one or more remote controllers, or "remuxes", and a connected serial multiplex link. The serial data link uses time division multiplexing for passing signals between the remuxes and the central controller. Because a large number of other loads may need to be serviced in such a system and because some may have a higher priority than others, it may be difficult or impossible to include a practical memory seat capability in the multiplex system due to the high traffic on the line and the requirement of the prior art systems to have substantially continuous access to their central controller.